Rails - Jan 2006 - date_select and sessions

i am using date_select to allow someone to select their birthdate in a
form.  however date_select uses 3 wierd labels in the forms like
follows:

<select name="user[birthdate(1i)]">
<option value="1940">1940</option>
<option value="1941">1941</option>
.

and then the month is user[birthdate(2i)] and so on.  My issue is i
dont know the best way to keep this data in a session (if there is a
user error on the form and want to keep data populated).  Also if
someone wants to edit their birthdate later on after a find() call,
how is this stored and later parsed by the form ?

thanks
adam